NASCAR Xfinity 500 takeaways: William Byron delivers walk-off win to advance to Championship 4

Needing a win to advance to the Championship 4 at Phoenix, William Byron put together a career performance and defeated Ryan Blaney late to pick up his third career win at Martinsville.

Here are three takeaways from the penultimate race of the NASCAR Cup Series season:

William Byron overcomes frustrating Round of 8 with Martinsville win

It was a flawless weekend for Byron, who swept the stages on Sunday after claiming Saturday's pole and moving Blaney out of the way with 43 laps remaining before pulling away after a late restart with 11 laps to go. The 304 laps led are a career-high for Byron, who entered Sunday's Round of 8 elimination race 36 points below the cutline and essentially in a must-win situation.

A bizarre incident with Ty Dillon at Las Vegas and a last-lap spin through the tri-oval at Talladega put Byron in the precarious position, but the speed has been there the last few weeks. He scored the second-most stage points at Las Vegas and restarted on the front row for the overtime finish at Talladega, but had nothing to show for the speed.

In his third consecutive Championship 4 appearance, Byron appears to be hitting his stride at the right time. As a past winner at Phoenix (spring 2023), Byron knows his way around the one-mile track and could be on his way to his first Cup Series title.

Team Penske will not win four consecutive titles

Since the Next Gen Car's inception in 2022, Team Penske has won the championship each season with Joey Logano (2022, 2024) and Blaney (2023). Despite a 31st-place starting spot, it looked like Blaney, who led the second-most laps in the race (177), would have a shot at keeping that streak alive with a third straight win in the Martinsville cutoff race.

Once Byron made the winning move around him with 43 laps remaining, he could not get back around him and had to settle for a disappointing runner-up finish. Logano was strong early, but came home eighth after trying a different strategy with 101 laps remaining.

Both drivers entered Martinsville needing a miracle to keep their title hopes alive after blowing a huge opportunity at Talladega. Considering the organization's strength on shorter, flat tracks like Phoenix, the Championship 4 drivers can breathe a sigh of relief that neither of them will be racing for the title next Sunday.

Kyle Larson claims final Championship 4 berth 

With their wins at Las Vegas and Talladega, respectively, Denny Hamlin and Chase Briscoe already secured their shot at a title coming into Martinsville. With Byron's impressive showing to claim the third spot, that left one more position to be filled on points between Larson and Christopher Bell.

Bell was one point to the good before the race started, but with six more stage points, a fifth-place finish was enough for Larson to advance by seven points over Bell, who finished seventh and missed out on the title race in heartbreaking fashion for the second season in a row.

With 35 races in the books, Hamlin, Briscoe, Byron and Larson will compete for a championship at Phoenix. With only one title between the four (Larson, 2021), a first-time champion could emerge when the dust settles in the desert.